1. Field
Example embodiments relate to nozzle plates, and more particularly, to nozzle plates for inkjet heads. Example embodiments also relate to methods of manufacturing the nozzle plates.
2. Description of the Related Art
Inkjet technology is being developed not only for graphics printing but also for fields such as industrial printable electronics and biotechnology. The inkjet technology may be easily applied not only to hard substrates but also flexible substrates such as plastic substrates. The inkjet technology may also reduce material costs. Additionally, the inkjet technology may be applied to new application fields such as flexible displays or low cost radio frequency identification (RFID) tags.
In order to apply the inkjet technology to fields such as printable electronics, relatively high printing speeds, relatively high drop positioning accuracies, and relatively minute droplet volumes may be required. However, these requirements are not easily met in piezoelectric inkjet heads or thermal inkjet heads of the related art. In particular, there are physical limitations in terms of realizing minute droplets having femto-level volumes with a high drop positioning accuracy because when the volumes of droplets are reduced to the level of femtoliters, the influence of drag force due to air resistance on the droplet speed is increased.
Electrohydrodynamic (EHD) inkjet heads for ejecting minute droplets are being researched. In some conventional EHD inkjet heads, a nozzle with a protruded structure is provided. In the conventional EHD inkjet head, droplet speeds and a volume of a droplet may be affected by an intensity of an electric field at an end portion of the nozzle. However, since an EHD inkjet head may use only one nozzle, it may be difficult to increase the printing speed. To solve this printing speed problem, a hybrid type inkjet head in which EHD inkjet technology and piezoelectric or thermal inkjet technology are combined has been developed.
In the hybrid type inkjet head, an intensity of an electric field may be increased at an end of each nozzle, and to this end, permittivity of a region around the nozzles may be reduced due to the nozzles having protruded structures. However, the nozzles having protruded structures are not only mechanically fragile but also cleaning of the nozzles is difficult if ink wetting is generated around the nozzles.